[E2E] PROMOTE TO BLOCKING: add_first_file_in_web_ide_spec.rb

What does this MR do?

Promotes the following e2e tests to the blocking bucket:

1. Create Add first file in Web IDE when a file with the same name already exists throws an error | Testcase | Spec metrics

This MR was created based on data from reliable e2e test report: #462605 (closed)

(This MR was automatically generated by gitlab_quality-test_tooling at 2024-05-20 02:05:37 UTC)